The present invention generally relates to semiconductors, and more specifically, to semiconductor fin patterning.
Device scaling drives the semiconductor industry, which reduces costs, decreases power consumption, and provides faster devices with increased functions per unit area. Improvements in optical lithography have played a major role in device scaling. However, optical lithography has inherent limitations for minimum dimensions, which are determined by the wavelength of the irradiation.
Directed self-assembly (DSA) is an alternative method for forming periodic structures, such as one-dimensional arrays of semiconductor line structures. In order to convert the array of semiconductor line structures into semiconductor fins, portions of the semiconductor line structures are etched away by employing lithograhic stacks. DSA of block copolymers (BCPs) employs a topographical or chemical guiding pattern to direct the BCPs into a desired morphology at a pre-determined location. BCPs are made up of discrete blocks of different polymerized monomers, or monomer blocks. The BCP material properties control the feature size and uniformity of the resulting structures.
In one example, di-block copolymers, for example polystyrene (PS)/poly(methyl methacrylate) (PMMA) BCPs can be used to pattern fins, with PS and PMMA blocks defining where the fins and spaces between the fins will be, respectively. Reactive ion etching (RIE) is then used to remove the PMMA block and reduce the critical dimensions (CD) of the fins to achieve the final fin CD.